As is well known, an electronic switching system (ESS) selectively connects two assigned subscribers out of many so as to establish a communications line between them.
Basic components of the ESS include a multiplicity of access switching subsystems, an interconnection network subsystem and a central control subsystem. Each access switching subsystem includes a plurality of subscriber interfacing units and a time division switching unit to communicate information between two selected subscribers. When the two selected subscribers are coupled to an access switching subsystem, they are connected within the same access switching subsystem. On the other hand, when the two selected subscribers are coupled to two different access switching subsystems, they are connected through the interconnection network subsystem. The interconnection network subsystem, coupled with each of the access switching subsystems and the central control subsystem, includes a central data link module and a space division switching unit and connects the two selected subscribers. Finally, the central control subsystem coupled with the access switching subsystems and the interconnection network subsystem controls all the operations and maintenance processes of the ESS.
The ESS further includes a line signal handling device which is coupled to the interconnection network subsystem and used to process a multiplicity of sets of line signals to be communicated between itself and at least one other ESS over designated channels of a plurality of trunks formed therebetween. As is well known, the sets of line signals represent control information employed for a call processing between the ESS and the other ESS.
According to E-1 type issued by a European Telecommunications Standards Institute (ETSI), each trunk combines N, e.g., 30, voice channels and P, e.g., 2, common signal channels, wherein N and P are positive integers, respectively. In the E-1 type, each of the thirty sets of line signals is communicated over one of the two common signal channels; and carries corresponding voice channel status information on all actions taken to make a call between the two ESS's. As is well known in the art, each of the line signals in said each set is normally transmitted for a separate predetermined range of time duration which is decided based on one of the conventional protocols, e.g., G. 704 issued by International Telegraph and Telephone Consultative Committee (CCITT). Through such communications of the multiplicity of sets of line signals, a call processing can be efficiently carried out between the ESS and the other ESS.
However, in such a line signal handling device provided in the ESS, any of the line signals in each set may be communicated between the two ESS's for a shorter or longer time duration than a predetermined range of time duration due to, e.g., a malfunctioning of a device or an error in any of the software programs incorporated in the ESS, thereby failing to provide a normal call processing. Consequently, it is desirable to analyze each of the line signals to be communicated between two ESS's selected from a plurality of ESS's and display information representing the status thereof on a display device.
Hitherto, no prior art ESS is known to have such analyzing and displaying capabilities.